The present invention relates to a high-speed transmission line system and, more particularly, to a line interface for a high-speed transmission line system.
It a common practice to provide a high-speed transmission line system with a line interface connected to a high-speed transmission line. The line interface is made up of an interface circuit for effecting an Alternate Mark Inversion/Transistor-Transistor Logic (AMI/TTL) or similar conversion, and a line state sensing circuit. Usually, a signal format on the high-speed transmission line has one period implemented as n time slots TS1-TSn and is maintained even after the high-speed line has been converted to internal lines by the line interface. Internal units incorporated in the transmission line system each transmit and receive data in one of the time slots TS on the internal lines. Hence, the time slot to be received by each of the internal units is determined on the basis of the location, internal arrangement and so forth of the unit. Each internal unit has n blocks for transmitting and receiving data in the time slots on the internal lines. Connected to the internal lines, the blocks each have a time slot selecting circuit for selecting a time slot, a data transmitting and receiving circuit for transmitting and receiving data in the time slot selected, and a logic circuit. Further, each block reports the time slot selected by the time slot selecting circuit to the data transmitting and receiving circuit which in turn reports such data to the logic circuit.
However, the conventional high-speed transmission line system, particularly a system having a plurality of time slot transmitting and receiving blocks in each internal unit, has some problems left unsolved. Namely, n identical time slot selecting circuits are built in each unit, resulting in wasteful circuit arrangement. Since the data transmitting and receiving circuits are connected to the internal lines and built in each internal unit, the individual unit consumes great current to thereby aggravate the current consumption of the entire system.